Author(s):
1. Diana Bogdan, Rudarski institut Prijedor, e-mail Save Kovačevića bb, Prijedor, Republic of Srpska, Bosnia and Herzegovina
2. Ljiljana Tankosic, Rudarski institut Prijedor, e-mail Save Kovačevića bb, Prijedor, Republic of Srpska, Bosnia and Herzegovina
3. Duško Torbica, Rudarski fakultet Prijedor, Republic of Srpska, Bosnia and Herzegovina

Abstract